Interpreting field data with engineering expertise — holistic geotechnical analysis from bearing capacity to liquefaction, settlement to foundation design.
Geotechnical survey and foundation engineering is the stage at which all the investigation and test data obtained from the field is interpreted with engineering expertise and turned into structure-specific foundation solutions.
By evaluating the field and laboratory results holistically, Geobim Engineering analyses in detail the bearing capacity, settlement behaviour, permeability and potential risks of the ground. The geotechnical investigation reports we prepare cover the definition of the soil profile, bearing capacity and settlement calculations, the assessment of groundwater conditions, liquefaction analysis and recommendations for a suitable foundation system.
These reports play a decisive role in the correct and safe design of important engineering structures such as bridges, dams, roads, tunnels, factories, residences, hospitals and schools. We carry out every survey by correctly establishing the relationship between the geological and geotechnical data and the structure, to the highest technical standards and in full compliance with current regulations.
Select any of the headings below to explore the details of the relevant analysis method.
01
Ultimate bearing capacity and allowable stress calculations based on soil parameters; determination of immediate, consolidation and total settlements.
02
CSR–CRR comparative liquefaction assessment based on SPT and CPT data; determination of ground behaviour and risk level under seismic loading.
03
Selection and sizing of shallow/deep foundations based on the soil profile, analysis results and structural loads; geotechnical investigation report in full compliance with legal requirements.
Bearing capacity analysis is the process of determining the critical stress limits so that structural loads can be safely distributed within the ground. Using the c (cohesion) and φ (internal friction angle) parameters obtained from SPT, CPT and laboratory data, Geobim Engineering calculates the ultimate bearing capacity (q_ult) with the Terzaghi, Meyerhof and Hansen relationships; it determines the allowable bearing stress (q_all) using a suitable factor of safety (FS ≥ 3.0) according to the structure type and safety class.
Settlement analysis covers the prior calculation of the vertical deformations that will occur in the ground under structural loads. The immediate (elastic) settlement S_i, primary consolidation settlement S_c and secondary (creep) settlement S_s are calculated separately to determine the total and differential settlement values. These values are compared against the allowable limit values (TS EN 1997) to ensure that structural elements are not damaged.
When insufficient bearing capacity or excessive settlement risk is identified, Geobim Engineering bases the decision to switch to deep foundation systems or ground improvement methods on an analytical foundation; it avoids unnecessary costs while never compromising on safety.
TS EN 1997-1 (EC7) · TBDY 2018 · TS 8853Elastic deformation occurring simultaneously with load application. The dominant component for sand and gravel; calculated from the elastic modulus E_s.
Occurs in clays through the gradual drainage of pore water over time. Calculated from the compression index C_c and the preconsolidation pressure σ'_p.
Slow, time-dependent deformation continuing after consolidation is complete. Significant in organic clays and high-plasticity soils.
Liquefaction is the phenomenon in which loose, saturated granular soils lose their strength during an earthquake due to rising pore water pressure and exhibit fluid-like behaviour. Since it causes sudden settlement, lateral spreading and loss of bearing capacity for structures, it is an inseparable part of ground investigation in seismic regions.
Geobim Engineering applies the CSR–CRR comparative analysis framework based on the Seed & Idriss (1971) and the current Youd et al. (2001) methods. The Cyclic Resistance Ratio (CRR) is determined from SPT (N₁)₆₀ or CPT q_c1N values; the Cyclic Stress Ratio (CSR) is calculated from the seismic load level (M_w, amax) to obtain the liquefaction factor of safety FS = CRR/CSR. For layers with FS < 1.0, the post-liquefaction settlement and sand-boil potential are also evaluated.
All analyses are conducted within the framework of the Turkish Building Earthquake Code 2018 (TBDY 2018) and using the site-specific spectral acceleration values from the Turkish Earthquake Hazard Map. When liquefaction is identified, the most suitable improvement method (DSM, jet grouting, vibro-compaction, etc.) is recommended on an analytical basis.
TBDY 2018 · Youd et al. (2001) · ASTM D1586The ratio of the cyclic shear stress induced in the ground by the earthquake to the vertical effective stress. It depends on magnitude and ground acceleration.
The soil's resistance capacity against liquefaction. Determined from SPT N₁(60) or CPT qc1N values through empirical correlations.
FS = CRR / CSR. FS < 1.0 indicates that liquefaction will occur; FS ≥ 1.25–1.30 is considered safe.
The expected volumetric compression and surface settlement in liquefied layers is estimated to evaluate the effects on the structure.
Once the geotechnical analyses are complete, the engineering assessment focuses on determining the optimum foundation system that will safely carry the structural loads. The choice between a shallow foundation (strip, raft), semi-deep foundation or deep foundation is based on analytical criteria according to the soil profile, structural load, acceptable settlement limits, environmental conditions and economic constraints.
The geotechnical investigation report prepared meets the standard format mandated under Turkey's building permit legislation (Planning and Zoning Law, TBDY 2018) and provides a complete technical basis for the building contractor and project engineers. The report findings and foundation recommendations are shared in coordination with the structural engineers throughout the design process.
TBDY 2018 · TS EN 1997 · Planning and Zoning Legislation
Specialised works carried out in addition to the main analyses depending on the project and the site.
The factor of safety of sloping terrain and excavation faces is calculated using limit equilibrium methods such as Bishop, Janbu, Morgenstern-Price and Spencer. Static and pseudo-static (seismic) conditions are evaluated separately; the critical slip surface is reported together with improvement options.
The time-dependent development of settlement is estimated with Terzaghi's one-dimensional consolidation theory. Using the drainage direction, layer thickness and the C_v coefficient, the % consolidation–time curve is plotted; the effectiveness of acceleration methods such as prefabricated drains is evaluated.
The water flow around the excavation, hydraulic gradient and uplift forces are calculated with flow nets and numerical methods. The need for a water cut-off wall, base heave control and drainage design parameters are determined.
Static pile capacity calculation with the α, β and λ methods; the end-bearing and skin-friction components are determined separately from Meyerhof and SPT–CPT correlations. Single and group pile behaviour is evaluated; a preliminary estimate is prepared for the load test programme.
Atterberg limits, sieve analysis, compaction, triaxial shear, consolidation, permeability and chemical content tests are carried out on the disturbed and undisturbed samples taken from boreholes, directly measuring parameters that cannot be determined in the field.
To determine the soil class (ZA–ZE) according to TBDY 2018, the weighted average shear wave velocity of the upper 30 metres, Vs30, is calculated. Where necessary, the site Vs profile is measured with the MASW / seismic refraction method; the local site amplification effect is evaluated.
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